The process of hydroforming is a metal forming process whereby specialized dies are used in conjunction with high pressure hydraulic fluid to force room temperature metal into the dies to form parts. An important application of hydroforming as used in the automotive industry is the creation of bent tubular parts. Many automotive bent tubular parts are produced utilizing a rotary tube bender, most commonly in the form of a “horizontal rotary draw bender”.
FIGS. 1 through 3 schematically depict a rotary tube bender in the form of a horizontal rotary draw bender 10, as known in the art, which includes a set of four dies: a bend die 12, a clamp die 14, a pressure die 16, and a wiper die 18. The bend die 12 is mounted to a stationary base 20, and is a forming tool designed to produce a particular radius of bend in the tubular workpiece 22 to be bent (compare FIGS. 1 and 3) per a concave radius 12a. The clamp die 14 is a tool designed to close securely upon the tubular workpiece 22. The pressure die 16 is used to press the tubular workpiece 22 into the bend die 12 via the wiper die 18, wherein the wiper die is a tool having a predefined curvilinear edge (see FIG. 4) which is shaped to abut the concave radius 12a of the bend die 12. The pressure die may also have a delayed (to avoid collision with the clamp die) “boost” or axial assist to push the tube forward during bending, which will feed material preventing a failure or rupture of the tube during the bending operation. The wiper die 18 is designed to prevent the formation of wrinkles or ridges in the tubular workpiece 22 during the process of its bending by the horizontal rotary draw bender 10, wherein an electronically controlled hydraulic rotation apparatus (not shown) is connected with the clamp die 14.
In this regard, FIG. 3 depicts the operation of the horizontal rotary draw bender 10 with respect to the bending of the tubular workpiece 22, which is inserted between the pressure die 16 and the wiper die 18 in interfacing relation with the bend die 12. The clamping pressure and rotation of the clamp die 14, while the pressure die 16 exerts pressure toward the wiper die 18 and bend die 12 and moves linearly forward toward clamp die 14 to prevent unnecessary elongation or tube failure, as provided by the hydraulic rotary apparatus, results in a bend 22a of the tubular workpiece 22 which conforms to the concave radius 12a (see FIG. 2) of the bend die 12. The wiper die 18 plays a significant role in the bending process of the tubular workpiece, whereby the wiper die ensures that no wrinkles will be produced while bending the workpiece, particularly at the inner radius of the bend.
As can be seen from FIGS. 4 through 5B, the wiper die 18 is composed of a wiper die holder 24 and a wiper die insert 26, which have mutually mating surfaces: a concave holder mating surface 24a and a convex insert mating surface 26a, which mating surfaces are complementing with respect to each other. The holder mating surface 24a has a raised boss 28 which is received by a complementary keyway (i.e., slot) 30 formed in the insert mating surface 26a. The wiper die 18 has a workpiece seating surface 34 having a concave radius for seating the convex outer surface of the tubular workpiece 22, wherein, in this respect, the wiper die holder has a holder workpiece seating surface 34a, and the wiper die insert has an insert workpiece seating surface 34b. The wiper die insert 26 is affixed to the wiper die holder 24 via, for example, a threaded fastener (not shown) threading at a bore 36 in the wiper die holder and the wiper die insert, wherein the bore is threaded at the wiper die insert portion thereof. At the distal end of the insert workpiece seating surface 34b is an insert edge 32 of the wiper die insert 26 which is of critical importance in the quality of the bend of the workpiece, via careful adjustment of the interface of the insert edge with respect to each of the bend die and the workpiece.
The insert edge 32 is the principal location of wear and its location is critical. In low volume production, a skilled operator can visibly detect when the wiper die insert 26 has become unsuitable to the point of needing replacement or adjustment. In a high volume setting, however, the traditional method of waiting for the workpieces to show evidence of this wear is inadequate.
Accordingly, what remains needed in the art is a means to monitor the location of the wiper die in the course of workpiece bending so that once the wiper die insert thereof has become unsuitable for production of bent tubular articles of sufficient quality, the operator will quickly and easily be enabled to detect this condition and render appropriate remedy.